1. Field of the Invention
The present invention relates to a method of converting the clock rate of a digitized signal, with essential characteristics of the signal itself being influenced via the clock-rate conversion.
2. Description of the Related Art
The present invention uses signal decomposition into subbands. A subband-signal-processing technique is described, for example, in EP-A-A 413 570 for picture data compression. Subbands are component signals which are associated with individual frequency ranges and are derived from the signal by means of a filter bank. By means of an inverse filter bank, the desired output signal, which is to come as close to the original signal as possible, can then be reconstructed from the individual subbands, which are modified if necessary.
Subband decomposition has been known for a long time for analog signal processing, but it is now of interest for digital signal processing since, because of the accuracy and stability of the digital filters and the remaining digital signal-processing circuity, no spurious signals are generated which cause signal distortion during the subsequent reconstruction or synthesis of the output signal. This applies to one-dimensional signals, such as audio signals, and two-dimensional or multi-dimensional signals, such as television signals.
The superposition of the horizontal and vertical scanning of the elements of an image corresponds to a two-dimensional video signal. If the continuous image sequence is taken into account as a third scanning sequence, this corresponds to a conventional three-dimensional video signal, with the scanning rates for the three dimensions being very different.